1. Field of the Invention
The invention relates to a single wafer type substrate cleaning method and a single wafer type substrate cleaning apparatus, more particularly to a single wafer type wet cleaning technique or system for applying a cleaning treatment to substrates such as semiconductor wafers one-by-one during the fabrication process, as well as certain devices such as electronic parts, and the like.
2. Prior Art
A so-called batch type wet cleaning system has been the principal method of cleaning substrates such as semiconductor wafers (hereinafter referred to simply as xe2x80x9cWafersxe2x80x9d), whereby wafers stored in a carrier cassette are immersed in sequence in wet bench type cleaning baths arranged in series, or wafers are directly immersed in the cleaning baths through a transfer unit without being stored in a carrier cassette. However, semiconductor devices have reached the sub micron age, in that they are now micro-fabricated and highly integrated, such that the face of wafers has recently required a very high degree of cleaning density, and wafers which are not stored in a cassette have to be wet-cleaned individually in a sealed cleaning housing. To this end, a so-called single wafer type wet cleaning system intended to meet the requirement of a higher cleaning density has been developed and proposed.
Under the single wafer type wet cleaning system, wafers can be cleaned with the use of a simple and compact cleaning apparatus in a relatively clean atmosphere where particles and the like do not settle or remain on the face of the wafer. This system is therefore practical to use for small scale production.
Generally, under the single wafer type wet cleaning system, a cleaning treatment is applied to the front face, i.e., the upper side surface of the wafer by various chemical fluids in a predetermined order. In the process, the chemical fluids supplied flow to the back face of the wafer, thereby possibly contaminating the back face of the wafer. If the back face of the wafer is contaminated, the handling jig for the wafer, e.g., the robot hands of a schalar type robot, also become contaminated, and as a result, other wafers which are handled by the same robot hands naturally also get contaminated.
For the foregoing reason, a technique for preventing the chemical fluid (s) from flowing to the back face of the wafer has become immensely desirable, and the device shown in FIG. 7 providing such technique has been proposed under Japanese Patent Laid Open Publication No. 2000-343054 (hereinafter referred to as the xe2x80x9cChemical Fluid Flowing Around Prevention Techniquexe2x80x9d).
Under the Chemical Fluid Flowing Around Prevention Technique, chemical fluid is supplied to the front face Wa of a wafer W while it is rotatably supported by a wafer rotary section xe2x80x9caxe2x80x9d, and simultaneously a certain gas is supplied from an annular nozzle xe2x80x9cbxe2x80x9d under the wafer W so as to float the wafer W while it is prevented from sliding sideways by a supporter member xe2x80x9ccxe2x80x9d, so that the chemical fluid which has flowed from the front face Wa of the wafer W to the back face Wb thereof is blown off as shown in FIG. 7(B).
However, the system of blowing off the chemical fluid through the supply of a gas prevents the back face Wb of the wafer W from being cleaned, thereby making it difficult to completely avoid contamination of the wafer. Accordingly, a further improvement of the system is desirable.
The present invention has been made in view of the aforementioned problem, and it is the object of the invention to provide a single wafer type wet-cleaning technique capable of effectively preventing chemical fluids from flowing to the back face of the wafer, which is not stored in a cassette, when the front face thereof is wet-cleaned by chemical fluids in a sealed cleaning chamber.
To achieve the above objective, the single wafer type cleaning method of the present invention for cleaning wafers which are not stored in a cassette, one-by-one in a sealed cleaning housing, comprises a cleaning step whereby various chemical fluids are sequentially supplied from above to the front face of each wafer, which is rotatably supported by the wafer rotary means in the cleaning housing, originating from supply nozzles located on the upper side of the cleaning housing, while purified water is injected and supplied to the back face of each wafer at the same time from a supply nozzle located on the lower side of the cleaning housing.
In the preferred embodiment, when purified water is injected and supplied in a radial direction from the lower side supply nozzle to the central portion of the back face of each wafer, which is rotatably supported by the wafer rotary means in the cleaning housing, the injected purified water cleans the back face of each wafer while it flows in a radial direction to the back face of the wafer owing to the centrifugal force generated by the rotation of each wafer. In addition, the injection and supply of purified water from the lower side supply nozzle is intended to cause the wafer to float owing to the force of injection and to reach the outer peripheral portion of the back face of the wafer owing to the centrifugal force generated by the rotation of the wafer.
The single wafer type cleaning apparatus of the invention is suitable for carrying out the foregoing cleaning method, and is designed to clean wafers, which are not stored in a cassette, one by one in a sealed cleaning housing, wherein the cleaning apparatus comprises (1) a wafer rotary means for supporting and rotating each wafer in the cleaning housing in the horizontal position, (2) a cleaning chamber provided at the outer peripheral portion of the wafer rotary means for forming a cleaning treatment space to clean each wafer which is rotatably supported by the wafer rotary means, (3) a chemical fluid supply means for supplying chemical fluids to the front face of each wafer which is rotatably supported by the wafer rotary means, (4) a purified water supply means for supplying purified water to the back face of each wafer which is rotatably supported by the wafer rotary means, wherein several chemical fluids are sequentially supplied from the chemical fluid supply means to the front face of each wafer from above, while the wafer is rotatably supported by the wafer rotary means, and at the same time purified water is injected and supplied from the purified water supply means to the back face of each wafer.
In the preferred embodiment of the invention, the purified water supply means has an injection nozzle for injecting and supplying purified water to the back face of the wafer which is rotatably supported by the wafer rotary means, wherein the injection nozzle is directed upward and located on the upper end portion of the rotatable rotary shaft of the wafer rotary means and can communicate with the purified water supply source. Further, the injection nozzle comprises a storage section communicating with the first and second passages and a number of injection ports located in the storage section.
Under the single wafer type cleaning system of the invention, several chemical fluids are sequentially supplied from the upper side supply nozzle to the front face of each wafer which is rotatably supported by the wafer rotary means while purified water is injected and supplied from the lower side supply nozzle to the back face of each wafer while the front face of the wafer is being cleaned by chemical fluids. As a result, it is possible to design a single wafer type wet-cleaning technique capable of effectively preventing the chemical fluids from flowing to the back face of each wafer when the front face of the wafer, which is not stored in a cassette, is cleaned by the chemical fluids in the sealed cleaning chamber. In the process, the chemical fluids that are supplied to the front face of each wafer flow toward the outer peripheral portion of the face of the wafer owing to the centrifugal force generated by the rotation of the wafer and are therefore prone to flow to the back face of the wafer. Accordingly, when the front face of each wafer is cleaned by chemical fluids, and purified water is injected and supplied to the back face of the wafer, the chemical fluids flow in a radial direction along the back face of the wafer owing to the centrifugal force generated by the rotation of the wafer, thereby cleaning the back face of the wafer. The purified water thus provides a sealing function relative to the chemical fluids which are prone to flow from the front face of the wafer to the back face thereof, and in the process effectively prevents the back face of the wafer from being contaminated by the chemical fluids.